Since the advent of personal computers, manufacturers have sought to integrate voice and data communication equipment. While early attempts at this integration met with mixed results, new products integrate all the functionality of a traditional phone with state-of-the-art, computer-supported switching systems, known in the art as private branch exchanges (PBXs).
One significant development in the art is digital transmission as the predominant method of signal transmission within a PBX. Digital techniques allow high-speed data transmission over twisted-pair wiring formerly used only for analog voice transmission. Integrated voice-data terminals, adapters within telephones, and stand-alone unit provide for sophisticated functions, such as simultaneous voice and data transmission.
A key element in development of digital PBX systems is digital signal processing (DSP) technology. A DSP unit is essentially a specialized microprocessor configured to process digitized analog signals. Unlike ordinary microprocessors, DSPs often have several paths of communication with peripherals, allowing them to do much of their system bus work without intervention by a CPU. They provide improved interrupt service and fast, real-time processing.
Telephone instruments have also evolved, becoming more intelligent and versatile. Most PBXs support industry-standard, single-line telephone sets with rotary dials or push-button, dual-tone multifrequency (DTMF) dial pads. The general trend, however, is toward proprietary electronic digital multibutton telephone sets with local microprocessors supporting enhanced features and functions. Such buttons can be programmed for different users, multiple line and trunk access from the same telephone, and alphanumeric displays that provide information about a call in progress.
PBX today often use multiple microprocessors for common control. A CPU or main microprocessor coordinates functions of other microprocessors and establishes call connections. Secondary microprocessors are located on other circuit cards and sometimes in electronic digital telephones.
Data transmissions switched through a PBX, and often through a local area network (LAN), can communicate with other data devices or computers connected to the system or via a public switched network, with a wide variety of remote data devices and computers. Modern PBXs offer features such as call forwarding, least-cost routing, station message recording, conferencing, hunting, and call restrictions.
FIGS. 1 and 2 show two PBX design options known to the inventors. FIG. 1 is an external block diagram of what might be termed a "Smart PBX" system. This design features one or more DSP cards in the PBX supporting voice mail, faxing, and other telecommunications operations. Control of the PCs is achieved through a LAN network. This Smart PBX allows efficient internal switching, it can use existing telephones, and voice mail and other functions are independent of the PCs, so they work even if a PC is not available. On the other hand, this solution requires major redesign of the PBX, with attendant development problems. There is also the expense of replacing the installed base of PBXs.
FIG. 2 is a block diagram illustrating another possible solution. In this system a DSP unit is provided in the PC as a separate module, such as an expansion card. Such a system would typically use an Integrated Services Digital Network (ISDN) interface between PBX and DSP. Specialized multimedia functions can be passed through to the telephone system.
The system of FIG. 2 can be built using existing cards, there is a relatively low investment in hardware, and there is a relatively low cost in providing the DSP by sharing the case and power with the PC. This design is not very suitable for workstations, however; the user must install the adaptor card; and the PC is not a good environment for analog circuits due to EMI and switching noise, for example.
At present there is no inexpensive and simple way to provide a state-of-the-art telecommunication system. The big deterrent to a Smart PBX system, as in FIG. 1, is the high cost of the PBX. And a telecommunications system where the DSP function is in the PC, as in FIG. 2, is not entirely suitable because PCs typically have limited space for adapters and installation of an adapter and setup is an inconvenience for the user. Moreover, PCs are an undesirable environment for analog circuits due to electromagnetic interference and switching noise.
What is needed is a solution wherein a user may conveniently add and replace functional modules as needed. This is provided in the present invention by making the telephone into the caretaker of the DSP and other functional modules. The only change required in the installed base is a new Smart Phone, which may be easily and quickly attached to both PC and PBX. Such an innovation allows for expansion into full-service, multimedia telecommunication.